The present invention relates to a communication system including a main phone (telephone) and a cordless handset wirelessly connected to the main phone.
Conventionally, a so-called cordless telephone connected to a public telephone line (hereinafter, occasionally referred to as an outside line) is provided with a cordless handset. In such a telephone, when a request signal to communicate with a destination telephone through the outside line is transmitted from the cordless handset to the main phone, if the main phone is used for a certain operation such as another outside line call, or transmitting or receiving facsimile data, signals are returned from the main phone to the cordless handset.
In the cordless handset, since no signals are transmitted from the main phone to the cordless handset in response to the request signal, a busy tone, which is usually output when there is a trouble in the wireless connection between the cordless phone and the main phone, is output. Because of the above configuration, the user cannot know, from the busy tone, whether there is a trouble in connection between the main phone and the cordless handset or the main phone is performing another function. If the busy tone was output due to an abnormal connection condition, the user may retry to connect to the main phone. On the other hand, if the main phone is performing another function, it would be better for the user to retry after a certain period has passed. However, in the conventional communication system as described above, the user cannot know the status of the main phone.